The present invention relates to a system for purging contaminants from a lens of an instrument, such as a radiation pyrometer, which provides for a uniform and efficient cleaning of the lens across its entire light transmitting surface.
It is well known to use radiation pyrometers for detecting temperatures in gas turbines or in similar applications, where the radiation is sensed through a window or lens that is adjacent the turbines. Contaminants accumulating on the lens have been a problem, and while more efficient arrangements providing asymmetric flow for purging the lens have been arrived at, such as that shown in U.S. Pat. No. 4,836,689, it has been found that even with an asymmetric flow, where there are flow disrupting bars that define peripheral inlets, there is a tendency for formation of "bubbles" of low air flow on the lens adjacent and in the lee side of the bars where particles will tend to accumulate.
Eliminating the divider bars between provided air flow slots has been a problem because of internal construction limitation, and the bars have not been recognized as causing low flow areas which inhibit removal of particles. The present invention improves the performance of purging systems by eliminating obstructions around which air must flow in path to the lens, and providing asymmetric purge flow.